Scientists develop sensor for homemade bombs
In a small but significant step in the battle against terrorism, scientists have developed an inexpensive chip capable of detecting hydrogen peroxide, the chemical used in the most common form of homemade explosives.
Hydrogen peroxide-based explosives were used in the 2005 bombing of the London transit system.
Researchers at the University of California at San Diego say the penny-sized electronic sensor, capable of sniffing out even tiny amounts of hydrogen peroxide, could also have industrial applications by monitoring toxic hydrogen peroxide levels in factories.
Details of the invention have been presented in the latest issue of the Journal of the American Chemical Society.
"The detection capability of this tiny electronic sensor is comparable to current instruments, which are large, bulky and cost thousands of dollars each," said William Trogler, one of its inventors.
"If this device were mass produced, it's not inconceivable that it could be made for less than a dollar."
The sensor works by monitoring the variability of electrical conductivity through thin films of "metal phthalocyanines". When exposed to most oxidizing agents, such as chlorine, these metal films show an increase in electrical current, while reducing agents have the opposite effect.
But when exposed to hydrogen peroxide, an oxidant, the metal phthalocyanine films behave differently depending on the type of metal used. Films made of cobalt phthalocyanine show decreases in current, while those made from copper or nickel show increases in current.
The team used this unusual trait to build their sensor. It is composed of thin films of both cobalt phthalocyanine and copper phthalocyanine to display a unique signature whenever tiny amounts of hydrogen peroxide are present.
Bombs constructed with hydrogen peroxide killed more than 50 people and injured 700 more on two London subway trains and a transit bus during rush hour on July 7, 2005.
More than 700 kg of a hydrogen peroxide-based mixture was discovered after an alleged bomb plot in Germany that resulted in the widely publicized arrest last September of three people.